Wear-resistant alloy



Dec. 11 1962 J. K. ELBAUM ETAL 3,068,096

WEAR-RESISTANT ALLOY Filed March 10. 1960 8 a ll Q g I u I 0 a. I l 8 5 l a; l- N I I E m I I E l 8 l I :2 W E o 1 a: I 8 i z l3 Ix a 8 7 J 1 I J O o O O O O o o o o 9 O -n v m N HElHWflN SSBNOHVH TIHNIBQ I INVENTORS JEROME K. ELBAUM EDWIN L. WAGONER ATTORNEY v United States Patent ()fiFice 3,068,096 Patented Dec. 11, 1962 1 2 3068 096 It is the primary object of this invention, therefore, to provide a nickel-base wear-resistant alloy which ex- WEAR'RESIQTANT ALLOY hibits high strength and hardness at both room tempera- Jemnie Elbaunt and Edvym Kokomo i ture and ele ated temperature which alloy contains a assignors to Umon Carbide Corporatlon, a corporation of New York lower amount of expensive and strategic materials than Filed Mar. 10, 160,Ser.No. 15,027 Present commerclal alloys;

1 Claim (CL 75 171 It 18 another ob ect of this invention to provide a nickelbase wear-resistant alloy possessing good impact re- This nvention relates to a nickel-base alloy suitable sistance, corrosion and oxidation resistance, and thermal for use in applications requirlng wear resistance. stability, which alloy may be used in castings and in hard- The special property of resistance to wear and abrasion surfaced deposits produced by welding. is required in machine components subjected to the cont is a further object of this invention to provide a tinual rubbing action of other movmg parts such as the nickel-base wear-resistance alloy suitable for use in valve valve seats in internal combustion engines. Because of eats in internal c mbustion engines, the need for wear resistance in many such applicat on In accordance with these objects, a wear-resistant alloy alloys have been developed Whlch eSPeC1a1lY eXh1b1t lihls is provided consisting essentially of from to percent p p ysuch y noted for then hardness, by weight chromium, from 5 to 12 percent by weight strength, and ability to retain hardness at elevated tern-- tungsten, from 10 to 17.5 percent by weight iron, from peratures. These wear-resistant alloys, most of which 0,8 to 1,6 percent by Weight carbon, up to 12 percent by have a cobalt-base, are used mainly in the form of cast- 20 Weight cobalt, from 5 to 12 percent by weight molybd lngs hard-suffacfid PQ Product?d y g- 5 num, and the balance nickel in a minimum amount of e y of thls yp have heretofore been 20 percent by weight and incidental impurities. Characteflzed y hlgh cost, low Impact resistance, allfl The alloy may also contain up to 1.5 percent by weight high strategic element content. In Table l thecomposrili d up to 2.0 percent by weight manganese. tlOHS Of typical commercial cobalt-base and nickel-base 2-5 Preferred eomposifigns of the alloy are set forth in wear-resistant alloys are shown. Table 2.

TABLE 1 TABLE 2 All cmstltuents AHOYA 30 Constituents A116 1 Alloy2 Alloy3 Alloy Alloyli Alloytl' Chromiun1 2s 26 26.27 26. 27 25.89 25.29 Carbm, 2 5 2,4 Tungsten 10 10 9. 64 11.77 9.32 9.32 Silicon 0.4 0.6 Iron....- 12.5 12.5 12.6 12.6 16.6 17.3 Mar t qnpqp 0, 7 0,2 Carbon-.. 1.6 1.4 1. 36 1. 36 1. 3 1. 3 Bornn 0.1 Manganese 0.4 0.2 0.16 0.16 0.18 0.18 Cobalt (1) 10 Molybdenum 5.3 10 9.8 10.72 9.6 0.6 Nickel 2 1 Silicon.-. 0.6 0.7 0. 64 0.64 0.77 0.77 mm 13.0 2 ,0 Cobalt 10 10 0. 49 0.49 10.36 10.36

Ni kel- (0 0) i efiif 40 1 Balance. Nickel-base alloys have not been used as widely as co- 'Ihe mechanical properties of these alloys and of the halt-base alloys (despite the less-expensive nature of prior commercial alloys previously designated Alloys A nickel-base alloys) because nickel-base alloys heretofore and B are shown 1n Table 3.

TABLE 3 Alloy N0. Mechanical Property Ultimate Tensile Strength, p.s.l 0,000 90,000 Hardness:

F., Rockwell "0 Test Reading 52 51 51 51 51 800 F., Brinell Hardness Number.. 425 1,000 F. Brinell Hardness Number 420 385 408 370 374 1,200 F., Brinell Hardness Number 385 364 371 354 373 1,400 F., Brinell Hardness Number 315 265 272 276 Impact Strength, Ft.-lbs 3-5 3-4 produced have not shown the hardness of the cobalt-base alloys. The cobalt-base alloy of Table 1, Alloy A, has a hardness corresponding to a Rockwell C test reading of 51-53, while the nickel-base alloy, Alloy B, has a hardness of only 42-44. It is to be noted that the hardness of a material is generally related to its wear-resistance characteristics. In the drawing, the hardness-versus-temperature characteristics of several alloys, including Alloys A and B, are shown. The graphs show the superior hot-hardness characteristics of the cobalt-base alloy. Since nickel-base alloys are generally less expensive and contain a lower strategic element content than cobaltbase alloys, the development of new nickel-base wearresistant alloys is avidly sought.

Some of the data presented in Table 3 is shown graphically in the drawing wherein the hardness-versus-temperature characteristics of new Alloy 2, and prior commercial alloys, Alloy A and Alloy B, are shown. seen that the nickel-base alloy of this invention has nearly the same room temperature hardness as the prior cobaltbase alloy, Alloy A, and has equivalent hot hardness characteristics compared to those of the cobalt-base alloy. In fact between the temperatures of 500 F. and 1100 F., the nickel-base alloy of this invention exhibits slightly superior hardness. It is to be noted that the superior hardness characteristics of the alloy of this invention compared to those of prior commercial nickel-base wearresistant alloys, such as Alloy B in FIGURE 1, are due to the novel composition of this alloy.

It is.

The special properties of this alloy are attributable to the critical composition wherein a number of carbides of the M C and M c types are present in a stable microstructure. The chromium present in this alloy contributes to oxidation resistance, strength, and hardness, both at room temperature and elevated temperatures. Tungsten, molybdenum, iron and cobalt enhance the strength and hardness of the alloy, along with chromium, mainly through the formation of carbides of both M C and M C types wherein M refers to atoms of metals from the group consisting of chromium, cobalt, molybdenum, tungsten and iron.

In reference to the hard carbide constituents, it is to be noted that the carbon content should not vary greatly from 0.8 percent to 1.6 percent. While carbon is essential in the alloy, many prior alloys contained higher carbon contents which would not favor this alloy. In the critical composition of this alloy at carbon content substantially over about 1.6 percent would result in a change in the hard carbide constituents in the microstructure from the M C and M C types to the M type carbide. While the M C type carbide is useful in resisting wear, its presence causes embrittlement of the alloy and thereby lowers the impact resistance. Furthermore, higher carbon contents change the character of the solid solution matrix of the alloy, causing a weakening and lowering of the ductility of the alloy.

As can be seen in Table 3, at low temperatures the cobalt content of from 0 to 12 percent cobalt may be replaced in whole or part by nickel. Thus Alloy 3, an essentially cobalt-free alloy having only 0.49 percent cobalt, exhibits a hardness and strength at low temperatures almost comparable to Alloy 2 which contains Manganese and silicon may be present in minor amounts in the preferred composition, but should not exceed 2 percent and 1.5 percent, respectively.

Of the two preferred compositions listed, it is seen that Alloy 2 has a higher hardness than Alloy 1. This is so because of the higher molybdenum content of Alloy 2, molybdenum being a particularly effective hardner.

The alloy of this invention may be prepared by standard metallurgical practices; and may be utilized in cast form or as a hard-surfacing material deposited by a welding operation wherein the welding rod is made of the alloy.

This alloy is suitable for any application requiring resistance to wear and abrasion and is particularly suited for service in valve seats in internal combustion engines. Having high corrosion and oxidation resistance, along with high hardness at elevated temperatures and good impact resistance, the alloy is suited for extended service as valve seat inserts exposed to the hot, corroding atmosphere found in internal combustion engines.

Another useful property possessed by this alloy is a high degree of thermal stability whereby parts composed of the alloy are able to withstand extended exposure to elevated temperatures without a change in dimensions or loss of surface soundness. To illustrate this property of the alloy, castings of a composition corresponding to Alloy 2 were exposed to an environment having a temperature of 1800 F. for 20 hours. Similar castings made from a prior commercial nickel-base alloy corresponding to Alloy B, were also tested. The results of these tests are shown in Table 4. The thermal stability of this alloy is believed to derive from the size and distribution of the carbides in the microstructure.

This application is a continuation-in-part of our copending application Serial No. 811,906, filed May 8, 1959.

TABLE 4 Change in Dimensions and Hardness Cha acteristics After 20 Hour Exposure to 1800 F.

Environment percent cobalt. However, at higher temperatures, on the order of 000 F. and above, Alloy 2, with a cobalt content of 10 percent, exhibits substantially improved hot hardness which permits up to 200 F. higher operational temperatures without loss of hardness.

The molybdenum and tungsten contents may be up to 12 percent of each. A high molybdenum and tungsten content is advisable when the cobalt content is very low. The molybdenum and tungsten contents then serve to help recover the slight loss of hot hardness in the alloy due to the reduction or absence of cobalt. Alloy 4 with high molybdenum and tungsten contents and lower cobalt contents, has hot hardness values substantially equivalent to those of Alloy 2 which contains 10 percent each of molybdenum, tungsten, and cobalt.

The iron content may be up to 17.5 percent. Alloys 5 and 6, which contain 16.6 and 17.3 percent iron, respectively, exhibit hot-hardness values comparable to the prior art high cobalt-low iron alloys.

References Cited in the file of this patent UNITED STATES PATENTS 1,520,033 MacGregor Dec. 23, 1924 1,587,992 Spitzley et al. June 8, 1928 2,214,810 Chesterfield Sept. 17, 1940 2,299,871 Baird Oct. 27, 1942 2,392,821 Kreag Jan. 15, 1946 2,955,934 Emery Oct. 11, 1960 

1.4 PERCENT BY WEIGHT CARBON, ABOUT 10 PERCENT BY WEIGHT COBALT, ABOUT 10 PERCENT BY WEIGHT MOLYBDENUM, ABOUT 0.7 PERCENT BY WEIGHT SILICONE, ABOUT 0.2 PERCENT BY WEIGHT MANGANESE, AND THE BALANCE NICKEL AND INCIDENTAL IMPURITIES. 